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Follicle-stimulating hormone (FSH) and oocyte secreted factors influence granulosa cell differentiation and follicle development. Whereas FSH stimulates the expression of mural cell transcripts, oocyte-secreted factors regulate specific cumulus cell genes and suppress the appearance of mural cell transcripts. The study addresses the extent to which clinically relevant changes in FSH doses applied during antral follicle development in vitro could alter the expression of oocyte and cumulus cells transcripts. A twelve-day culture system in which mouse ovarian preantral follicles can grow up to preovulatory follicles was used. Three FSH regimens were considered: 1) a continuous exposure to 10 mIU FSH (control); 2) decreasing concentrations of FSH (Low FSH) and; 3) 25 mIU FSH (high FSH) as soon as antrum is formed. In oocytes: Gdf9, Bmp15, and Fgf8, and in cumulus cells: Amh, Lhcgr, Ar, and Pfkp transcripts were quantified by real-time PCR. In high FSH, the three oocyte transcripts were up-regulated, while in cumulus cells a shutdown of the Amh signal and substantial increase of Lhcgr and Ar expression were measured. In contrast, low FSH tended to reduce Lhcgr to levels comparable to in vivo. Levels of Pfkp were not affected by FSH doses. These results demonstrate that a 2.5-fold increase of FSH changes both oocyte and cumulus cells transcripts levels. Conversely, a decrease of FSH does not affect transcripts levels, but seems to limit an inappropriate Lhcgr expression. Modulating FSH within physiological ranges during the antral phase of culture alter cumulus cells differentiation. |
